Do Chaoborus larvae migrate in temporary pools?

A diurnal vertical migration of larvae of Chaoborus punctipennis (Say) was observed in shallow temporary woodland pools in East Texas. In the laboratory, in 153 cm tall columns, the larvae underwent a much greater migration than possible in the shallow pools. We hypothesize that the migratory behavior and transparent body of Chaoborus larvae may have originally evolved in such shallow water habitats. These traits enabled Chaoborus to successfully invade the quite different adaptive zone of predation in the plankton of deep lakes.     

Photochemical cross-linking of the Escherichia coli single-stranded DNA-binding protein to oligodeoxynucleotides. Identification of phenylalanine 60 as the site of cross-linking

The single-stranded DNA-binding proteins from bacteriophage T4, F plasmid, Escherichia coli, and calf thymus can all be covalently cross-linked in vitro to thymine oligonucleotides by irradiating the respective protein-oligonucleotide complexes with ultraviolet light. More extensive studies on the E. coli single-stranded DNA-binding protein (SSB) indicate that this reaction is dependent upon both the length of the oligonucleotide and the dose of ultraviolet irradiation. Using anion-exchange and reverse-phase ion-pairing high-performance liquid chromatography we have isolated a specific cross-linked tryptic peptide comprising residues 57-62 of the SSB protein with the sequence valine-valine-leucine-phenylalanine-glycine-lysine. Solid-phase sequence analysis of the covalent [32P] p(dT)8-peptide complex indicates that phenylalanine 60 is the site of cross-linking. This amino acid is located within the general region of SSB (residues 1-115) that has previously been shown to contain the DNA-binding site (Williams, K. R., Spicer, E. K., LoPresti, M. B., Guggenheimer, R. A., and Chase, J. W. (1983) J. Biol. Chem. 258, 3346-3355). The high-performance liquid chromatography purification procedure we have devised to isolate cross-linked peptide-oligonucleotide complexes should be of general applicability and should facilitate future structure/function studies on other nucleic acid-binding proteins.     

Streptococcal Fc receptors. II. Comparison of the reactivity of a receptor from a group C streptococcus with staphylococcal protein A

The reactivity of a soluble Fc receptor from a group C streptococcus ( FcRc ) was compared antigenically and functionally with the staphylococcal Fc receptor, protein A. Protein A and FcRc were found to inhibit each others' binding to the Fc region of human IgG, indicating that they bind to sites that are in close proximity on the Fc region of human IgG. The two bacterial Fc receptors were antigenically unrelated. Differences were observed in the species and subclass reactivity of the two receptors. The patterns of binding of protein A and FcRc under various conditions suggested that these receptors reacted with distinct regions on the Fc region of immunoglobulins. FcRc bound more efficiently to goat, sheep, and cow IgG, protein A bound more efficiently to dog IgG, and neither receptor bound to rat IgG. Differences were also observed in the reactivity towards human IgG subclasses. The FcRc bound to all samples of the four human IgG subclass standards. Protein A bound to IgG1, IgG2, and IgG4, and to one of two IgG3 myeloma proteins tested. The reactivity of our soluble FcRc corresponds to a type III streptococcal Fc receptor classified by the reactivity of intact bacteria.     

IgE immune complexes induce immediate and prolonged release of leukotriene C4 (LTC4) from rat alveolar macrophages

Alveolar macrophages obtained by lung lavage from rats were incubated with monoclonal mouse anti-DNP IgE and specific antigen (DNP-HSA) and were found to release a slow reacting substance (SRS), which was characterized by high performance liquid chromatography as leukotriene C4 (LTC)4. Alveolar macrophages incubated with 1 microM A23187 (calcium ionophore) released similar amounts of SRS (6.0 +/- 2.2 and 5.7 +/- 3.7 X 10(-10) mol of LTC4 per 5 X 10(6) alveolar macrophages, respectively). The optimal conditions and mechanism of LTC release by IgE and antigen were examined. LTC4 release was maximal when freshly retrieved alveolar macrophages were incubated for 20 min with 10 micrograms/ml IgE and then for 20 min with 100 ng/ml antigen or for 20 min with IgE and antigen that had been preincubated together for 30 min at room temperature. In addition, LTC4 release was maximal when cells were challenged with IgE and antigen in a protein-free balanced salt solution and when the cells were tumbled to prevent adherence. Dose response experiments revealed that macrophages released LTC4 when stimulated with as little as 10 ng IgE and 100 ng DNP-HSA. Alveolar macrophages did not release LTC when challenged with IgE or DNP-HSA alone. Activation of LTC4 release by IgE and antigen was rapid in onset (2.5 to 5 min), and washing to remove fluid phase IgE and antigen revealed that once activated, alveolar macrophages were capable of prolonged and continuous release of LTC4. Peritoneal lavage cells stimulated with IgE and antigen did not release SRS but could release SRS when incubated with A23187 (5.7 +/- 1.3 X 10(-10) mol LTC4/5 X 10(6) macrophages). A large variability existed between individual rats in the ability of their alveolar macrophages to be activated by IgE and antigen to release LTC4. DNP-HSA labeled with 125I was used to show formation of immune complexes of IgE and antigen when IgE and antigen were incubated together before macrophage challenge. IgE immune complexes containing as little as 2 ng of antigen elicited the release of LTC4 from alveolar macrophages. These data indicate that rat alveolar macrophages release primarily LTC4 when challenged with IgE immune complexes, and that the alveolar macrophage may differ in this respect from peritoneal macrophages that do not release detectable quantities of LTC4 when challenged under identical conditions.     

Streptococcal Fc receptors. I. Isolation and partial characterization of the receptor from a group C streptococcus

A receptor for the Fc region of immunoglobulin G was extracted from a group C streptococcus, purified and physicochemically characterized. The Fc receptor was extracted in high yield by lysis of the bacteria after infection with bacteriophage. The soluble receptor was purified to functional homogeneity by sequential chromatography on cellulose phosphate, DEAE, and selective elution from a column of immobilized human IgG. Four hundred micrograms of the functionally pure protein was obtained per gram (wet weight) of bacteria extracted. The affinity-purified receptor was functionally homogeneous in binding to the Fc region of human IgG; however, the product was heterogeneous on both non-denaturing and SDS polyacrylamide gels. Four major protein bands were observed, with the predominant form of the Fc receptor having an m.w. of 64,000 daltons. Antibody prepared against the major Fc receptor protein ( FcRc -II) was capable of reacting with all the fractions and completely inhibiting functional activity. The results of the competitive binding studies suggest that the purified Fc receptor behaves as a single receptor, and that the differences in charge and size were probably due to covalently bound cell wall constituents.     

Decreased triiodothyronine binding to isolated nuclei from livers of preobese and obese (ob/ob) mice

L-Triiodothyronine (T3) binding to hepatic nuclei from (ob/ob) mice at different ages was examined and compared with that of lean controls. Results showed a significant reduction in T3 binding in liver nuclei of obese mice at all ages studied. The preobese mice at 2 weeks of age had 27.9% fewer receptor sites/mg DNA compared to lean controls, receptor concentration further decreased to 67.7% at 18 weeks of age. Data presented here demonstrates that the impaired triiodothyronine (T3) binding to hepatic nuclei present in older (ob/ob) obese mice is an antecedent to the obesity. This report also helps to explain the poor thermoregulation and low oxygen consumption present during the preobese phase of the postnatal development of these animals.     

Isolation and partial characterization of a type II Fe receptor from a group A streptococcus

A group A streptococcal strain rich in Fc receptors was selected by an immunoblotting technique and used as the source for isolation of a functionally active Fc receptor. A variety of extraction techniques were compared including (1) heat extraction at neutral, acid or alkaline pH, (2) treatment with the enzymes mutanolysin, hyaluronidase, trypsin, papain or phage lysin, or (3) autoclaving or heating in the presence of sodium dodecyl sulfate. The most homogeneous receptor was recovered following heat extraction and contained two molecular weight forms. The major form had a molecular weight of 56 000 daltons and the minor form had a molecular weight of 38 000 daltons. These two proteins could be isolated without loss of activity by binding to and elution from a column of immobilized human IgG. An antibody prepared against a single form of the affinity purified receptor demonstrated reactivity with both molecular weight forms of the heat extracted receptor. The group A receptor was found to be both antigenically and physicochemically distinct from either the type I receptor found on the majority of Staphylococcus aureus strains or the type III Fc receptors found on the majority of group C streptococcal strains.     

Ventilation rate and arousal in the Octopus

Observations on undisturbed, individually isolated, Octopus vulgaris Cuvier show that ventilation rate is strongly related to “arousal” or activation. Ventilation rate may be recorded visually by a screened observer or remotely, using carbon electrodes connected to a pen recorder via an impedance coupler to register the associated water movements in a small experimental chamber. The method allows a quantifiable behavioural characteristic to be measured objectively. It has been used to demonstrate that O. vulgaris responds to certain chemical stimuli in flowing sea water with a sharply increased ventilation rate. This result is taken to show distance chemoreception in this cephalopod.     

Melting order of successively longer yeast phenylalanine-accepting transfer ribonucleic acid fragments with a common 5' end

Temperature-jump methods were used to study the kinetics of the helix to coil transition in three fragments of yeast tRNAPhe that share a common 5' terminus (the 5' end of the mature tRNA). Correlation of the extrapolated helix dissociation time constants with NMR exchange broadening results allows assignment of the structural basis of the optical melting transition in the fragments. The results confirm nuclear magnetic resonance findings on these fragments: the 5' 1/4 fragment has no helical structure; the 5' 1/2 fragment contains the D stem; and the 5' 3/5 fragment contains the D stem and the anticodon stem. These are the structures expected if sequential folding of the tRNA during biosynthesis were to occur. The D stem is the last helix to melt in the 5' 3/5 fragment. We suggest that structural elements in addition to the four Watson-Crick base pairs of the D-stem helix are responsible for the anomalously high Tm of that hairpin.     

A model of the role of natural killer cells in immune surveillance — II

The functioning of natural killer (NK) cells as immune surveillance effector cells against tumors is explored. In part I (J. Math. Biol. 12, 363-373 (1981], it was predicted that susceptible tumors would be eliminated if they have parameter lambda 0 value negative. They would not be eliminated if lambda 0 greater than 0. As the lambda 0 less than 0 result was local, one expected either that tumors of all sizes with lambda 0 less than 0 will be eliminated (global stability) or that tumor population will go to zero if in a domain of attraction of the critical point which is not all of the positive orthant. In this paper, the second is shown to be true. The general results are illustrated by a specific model.